The invention relates to a process and an apparatus for removing tin, arsenic and antimony from molten lead by means of oxygen or oxygen-containing gas mixtures, which is or are blown into the molten lead by means of at least one gas nozzle.
Various processes are already known for the refining of molten lead, in order to remove tin, arsenic and antimony.
The Harris process uses caustic soda and saltpetre as oxidizing agents. By means of a pump, the molten lead to be refined is pumped over into an intermediate vessel, the precipitated oxides being obtained in a salt slag. The slag then requires expensive further processing.
In the open-hearth process, air blown in is used for the oxidation. The resulting large quantities skimmed off at low antimony contents require expensive processing.
A refining process described in DE 3,327,796 Cl uses oxygen-enriched air in the melting vessel. In the process described, the rate of refining is limited by the lead temperature of 650.degree. C. in the vessel. For slag formation, small quantities of caustic soda are added. Higher melting temperatures and working without caustic soda are possible in a refining process according to DE 3,831,898 Cl. In the process described, oxygen is introduced into a turbulent flow of molten lead, concentrated into a part volume relative to the melting vessel. The lead intimately mixed with oxygen enters a larger volume for relaxation, where the oxides float up and are skimmed off. The turbulent stream of lead is generated by a lead pump which delivers the lead into a reaction tube. The reaction tube is arranged in a second cylinder of larger volume, from which the oxides are taken off. The lead flows out through-an outlet orifice located at the bottom.